In a distribution conveyor system, conventionally, an object to be transported (a baggage, or a container) can be identified by attaching, by means of an auto labeler, an adhesive label, to which necessary information, such as shipping address, and barcode, is printed, to the object transported by a conveyor.
Recently, a reversible thermosensitive recording medium, which colors and erases with heat, has been applied as a label for a transporting container for a distribution conveyor system, in view of energy saving, and protection of the environment. Systems for printing an object to be transported (an irradiation target) in a non-contact manner using a laser device have been proposed (see, for example, PTL 1).
Laser light used for label printing in such a system is extremely strong, and may burn or damage eye sight, if the laser light is directly applied to skin or eyes of humans. Accordingly, a protection barrier is installed in a working environment where people may come close to a laser device during printing, in order to adjust the laser exposure to human bodies to a safe level.
As for the protection barrier, a member having a relatively large surface roughness, which is typically prepared by applying surface coating onto a metal plate, is typically used in order to facilitate laser light applied to be absorbed, or diffuse reflected. Laser light emitted from a laser device needs to be reflected at least twice or more, to reduce the intensity of regular reflection light of laser light to a safe level to human bodies. Specifically, it is necessary that the protection barrier has a structure with which primary reflection light is not released to the outside.
However, a reflection direction of primary reflection light generated by reflecting laser light emitted from a laser device on an inner surface of a conventional protection barrier is not considered, when an object to be transported is not present. Accordingly, there is a problem that a scale of a protection barrier is increased, of the protection barrier has a structure with which primary reflection light is not released to the outside.